Amphipods and Copepods

Nick Dakin

Amphipods are a catch-all title for tiny crustaceans generally found feeding amongst the detritus at the bottom of an aquarium, within the filters, or even on the front glass. They are easily identified as shrimp-like creatures up to one centimetre in length, half-moon in shape and grey in coloration.

Amphipods rarely do any damage; however, it is suspected that some species are carriers of certain fish diseases, although this has yet to be fully proven. They are quite hardy and fully capable of reproducing to plague proportions should conditions prove favourable. Rather than being dangerous, a plague of Copepods is more unsightly and alarming to those inexperienced in such matters.

Copepods are similar in habit to Amphipods, although they are much smaller (not much bigger than a few millimetres), and are distinctly different. Plagues of both animals can only proliferate where there is enough food and this can usually be traced back to an over-enthusiastic hobbyist providing far too much at feeding time.

The Solution

In the long term, a drastic reduction in the amounts of food offered to both fish and invertebrates will see a steady decline in numbers to almost zero.

An immediate cure would be to remove the creatures by siphoning them off. They will be found congregating under rocks during the daytime or clinging to the glass and a quick hand will be necessary to allow for a surprising turn of speed!

Many fish would enjoy a Copepod feast if they could have access to their hiding places which, often as not, prove to be unreachable. Therefore, regular disturbance may assist in reducing numbers as the fish learn to pick them off.